Rearing tank for aquatic animals

Claim 2

Apparatus for maturing movable aquatic animals comprising a liquid containing tank with a top open to the environment for holding fluid, a plurality of platforms of foraminous material located within said tank across which the animals can move unobstructed, means for stacking said platforms spaced vertically one above the other, and means located below the lowermost platform of the stack of platforms for circulating the liquid through the tank while filtering the same, the filtered liquid passing upwardly through said platforms.

Claim 3

Apparatus as in claim 1 wherein said platforms are substantially flat.

Claim 4

Apparatus as in claim 1 wherein said platforms slope upwardly from the center.

Claim 5

Apparatus as in claim 1 wherein said foraminous material for each of said platforms comprises a net.

Claim 6

Apparatus as in claim 1 wherein said circulating means has an outlet generally in the central area of the stack of platforms.

Claim 7

Apparatus as in claim 1 wherein said circulating and filtering means comprises an air lift filter system including a filter media at the bottom of the liquid of the tank, a conduit having a first portion with an inlet adjacent the bottom of the tank, and a second portion having an outlet beneath said filter medium, means for supplying gas under pressure to said first portion of said conduit to convey liquid from the inlet to the outlet of the conduit, the liquid discharged from the outlet passing upwardly through the filter media back into the tank.

Claim 8

Apparatus as in claim 6 further comprising means for permitting the escape of trapped gas from below the filter media into the fluid of the tank.

Claim 9

Apparatus as in claim 6 further comprising means for bleeding the gas from the conduit.

Claim 10

Apparatus as in claim 8 wherein said means for bleeding the gas comprises a third portion of said conduit located above the liquid level of the tank and having gas discharge means thereon.

Claim 11

Apparatus as in claim 1 further comprising means attached to said plurality of platforms for collapsing the stack of platforms together.

Claim 12

Apparatus as in claim 10 wherein each said platform comprises a frame on which the foraminous material is located and said collapsing meaNs comprises a first line attached to the bottom frame and passing through a fixed point of all of the other frames, and a second line fixedly attached to each of the other frames.